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?Tom Hull? - ?Google ????? 3D model is indispensable in ship design and manufacturing. However, there are scarce constraints on the parameters of these 3D ship models and few correlations between the different ship model parts. Therefore, it will cause additional work when we modify our models myboat294 boatplans: Liu. Jian, Shichao. Zhang, Liumin. Tian, Deyu. Wang. A. I. Ginnis, C. Feurer, K. A. Belibassakis et al., �A CATIA� ship-parametric model for isogeometric hull optimization with respect to wave resistance,� in Proceedings of the International Conference on Computer Applications in Shipbuilding , vol. 1, pp. 9�20, Italy, View at: Google ScholarAuthor: Yu Lu, Xin Chang, Xunbin Yin, Ziying Li. Sep 15, �� Fig. 3 shows the tasks of the design manager in the ship hull production design part without a process after the arrival of the �Main Deck Const.� drawing of the �S02� project which is the light aircraft carrier of 20, t displacement. Download: Download full-size image; Fig. 3. Tasks of the ship hull production design part manager.
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However, this knowledge expression method is not good enough at expressing the relationships between hull Model Ship Building Forum Uk Google Play components such as hierarchical relationship, spatial position relationship, etc. At the same time, it should be noted that the way of knowledge expression in the above research is not once and for all, that is to say, by using the production expression method to embed the knowledge into the computer, we can easily build the 3D models of the ship structure that meet the requirements. However, with the continuous advancement of manufacturing process, the semantic information implied in the 3D models still needs to be repeatedly embed and parsed, these embedding and parsing of knowledge are sometimes necessary, but more often cause repeated and meaningless work Lee, Lee, Roh, Sign In or Register.

Advanced Search. Sign In. Skip Nav Destination Proceeding Navigation. Close mobile search navigation. All Days. Previous Paper Next Paper. Article Navigation. Jian ; Liu. This Site. Google Scholar. Zhang ; Shichao. Shanghai Waigaoqiao Shipbuilding Co. Tian ; Liumin. Wang Deyu. Published: October 11 International Society of Offshore and Polar Engineers.

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Please check your username and password and try again. Section 3 is devoted to the prediction method of the total resistance performance, which has been defined as the optimization objective function in this work. The ITTC model-ship correlation formula and the Rankine source panel method are applied to calculate the frictional resistance and wave-making resistance, respectively.

The Rankine sources method is based on the potential-flow without considering viscosity. Nevertheless, for a sophisticated ship-hull optimization system, it is more simple and convenient and has been proved to be accurate, reliable, and efficient, so it has been investigated in various studies Abt and Harries et al.

In , Holland [ 32 ], a professor of Michigan State University, firstly proposed Genetic Algorithm GA , which is a computational model simulating evolutionary process in nature.

Deb et al. Finally, two optimization cases for KCS [ 35 � 37 ] are set up and presented in Section 5. The first case deals with a ship-hull optimization at design speed, while the second case involves a total resistance minimization problem against multiple objective functions covering all speed range. In this article, the hull form transformation is realized by the fairing B-spline parametric curve transformation. The deformation of B-spline parametric curves is realized by adjusting the input characteristic parameters, and then the deformation of the characteristic parameter curve is mapped to the geometric deformation of the hull.

The fairing B-spline parametric curve is formed by applying the constraint conditions on a B-spline curve. The spatial spline curves parameterized by are expressed by : The equation corresponding to the curve with mth fairness can be expressed as Some control constraints should be satisfied in the fairing process.

The Euler formula is used to express the distance between the control point and the spline curve. The distance shall meet the following condition: where is distance weight and is a tolerance greater than zero. The area under the spline curves should meet the condition of the fixed value; that is, where is a given area.

At the same time, if necessary, other conditions can be taken into account in the same way mentioned above to complete the corresponding constraints. This section shows how to realize the deformation of the transverse section lines by the fairing B-spline parametric curves. This method is also applicable to other lines of the hull. The hull geometry model is stored in the form of offsets; that is, the hull is discretized into a finite number of transverse section lines.

Thus, the displacement variations of all points on the B-spline curve can be mapped to the ship hull curve with the same original coordinates. For the B-spline parametric curve itself is highly fairing, while being mapped to the hull, the hull geometry deformation must also be fairing.

In the process of hull form transformation one or more of the fairing B-spline curves can be applied as deformation weights to avoid the geometric distortion. Similarly, assuming that and are the maximum variations of the curves in the Y direction and the Z direction, since they are used as weight functions, and should meet and , respectively.

Thus, the coordinate displacement formula of the points on each transverse section line can be expressed as where and represent the weight value of the displacement variation of the point on the fairing B-spline curve with the same original coordinates as the corresponding point on the hull surface when the input parameters are and.

The total resistance can be calculated by the empirical formula as follows: where is the total resistance coefficient and is the wave-making resistance coefficient which can be obtained by the Rankine source method.

Taking the o-xyz as the Cartesian coordinate system fixed on the ship, the X-axis is in the direction and the Z-axis is perpendicular to the surface of the water. The Y-axis is determined by the right hand rule. Assuming that the ship speed is , because of the motion of the hull, the velocity potential and perturbation potential with the free surface effect constitute the total velocity potential of flow field around the ship, whose expression is.

In the potential flow, the ideal fluid is nonviscous, incompressible, and nonrotating. Then in the fluid computational domain the total velocity potential subjects to the Laplace equation and the following boundary conditions:.

This is where the subscripts denote the partial derivatives and is the gravitational acceleration. This is Employ the Rankine source panel method by the iteration procedure to solve the above boundary conditions.

Once the velocity potential is resolved, the free surface wave elevation can be obtained. In addition, through the instrumentality of the Bernoulli equation, the pressure coefficient at each panel can be defined as where is the Froude number with the expression,.

It has been selected as the standard form of CFD results validation by Goteborg ship CFD symposium and Tokyo ship CFD symposium, with a wealth of open test data and a large number of numerical results. The principal dimensions are listed in Table 1. The body plan, the side view, and the mesh generation are shown in Figures 1 , 2 , and 3 , respectively. There are hull surface meshes and free surface meshes. According to the calculation method of the ship total resistance mentioned above, five speed points are selected for the hydrodynamic resistance performance evaluation and the corresponding calculation conditions are consistent with the ship model test data published in the ship hydrodynamic CFD symposium.

Comparison of the total resistance coefficient between the calculated results and the open test results is shown in Figure 4.

It can be seen from the figure that the numerical results are in good agreement with the open test results. Comparisons of wave profile and longitudinal wave cuts profiles between the calculation results and test results are shown in Figures 5 and 6 , respectively, which also show that the calculated results are in good agreement with the experimental results.

The wave pattern calculated is shown in Figure 7. The comparative analysis shows that the empirical formula combined with the Rankine source method based on the potential flow theory to predict the resistance performance of ship has a high reliability, which can meet the requirements of ship hull optimization well.

The optimization strategy is a critical part of the resistance optimization design methodology for bow and stern line. A large number of studies related to the optimization strategies have been explored and implemented for the ship design.

In this study, the NSGA-II Nondominated Sorting Genetic Algorithm is used as the resistance optimization algorithm for searching for the optimal hull form with a minimal ship total resistance considering all speed range.

The fast nondominated sorting method is implemented. Each individual is set with two attributes and. The former is the set of solution individuals dominated by the individual ; the latter is the number of solution individuals that dominate the individual i.

Then, for each individual j in the current set F 1 , every individuals set dominated by individual j is examined. The of each individual belonging to individuals set is decremented by one. Finally, the same nondominated rank is assigned to all the individuals within and the same process continues until all individuals are graded. In order to ensure the diversity of the population in the process of optimization calculation, the technology of density estimation is employed, representing the density of any individual as crowding distance , that is, the smallest cube containing only the individual.

When is smaller, it means that the feasible solutions are concentrated around an individual. For maintaining the diversity of the population, an operator for density estimation and the crowded comparison is needed to ensure that the algorithm can converge to a uniform distribution of Pareto-optimal front. After sorting and crowded comparison, any individual in the population has two attributes, nondomination rank and crowding distance.

A random parent population P 0 is created initially. Then a combined population is formed in which the t th is the generation of the proposed algorithm; therefore the population will be of size 2 N.

The population is sorted according to nondomination. The new parent population is formed by adding solutions from the first front till the size exceeds N. This population of size N is now used for selection, crossover, and mutation to create a new population of size N. The implementation of the hydrodynamic optimization system required the use of three main components presented above, namely, the hull form transformation, the resistance prediction by Rankine source method, and the optimization strategy.

Through the analysis and establishment of hull form optimization model proposed above, the optimization design process of hull lines is shown in Figure 9. The total resistance at the design speed is used as the optimization goal: where is the total resistance coefficient of original hull and is the total resistance coefficient of the feasible solution in the optimization process. Because the KCS ship has a larger bulbous bow as well as a complex shape of stern surface, when it is sailing, the first shear wave and the tail wave will interfere with each other after the ship.

The interference may be beneficial or harmful to wave making resistance. Therefore, the bow and the stern are selected as the optimization design area, as shown in Figure A total of 7 variables are set for the bow area, that is , , , , , , and which are mainly used to control the expansion changes of bulbous bow in the direction of X axis, the harmomegathus changes in the direction of Y axis, the translational changes of the bow in the direction of Z axis, and the precursor smooth transition between bulbous bow and hull.

A total of 3 variables are set for the stern area, which are , , and mainly used to control the translational changes of the stern in the direction of Z axis, the sag Model Ship Building Hull Planking 40 at the upper end of the stern, and the uplift of the lower end of the stern. The different types of transformation for the KCS ship in offsets circumvented with the above 7 variables are shown in Figures 11 � 17 , where original hull lines are marked with red and the transformed hull lines are marked with blue.

The constraint conditions on the 10 design variables that control the translation of the hull are listed as follows: 2 Optimization Results for Single Design Speed. The convergence courses for the objective function and various design variables are shown in Figures 18 and 19 , respectively.

The convergence course of single design speed optimization for various design variables: a dx 1 , b dy 1 , c dy 2 , d dy 3 , e dy 4 , f dz 1 , g dz 2 , h dz 3 , i dz 4 , and j dz 5. As shown in Figures 18 and 19 , the objective function and design variables are convergent in the last iteration.

The final convergence solution is marked by the red boundary line, denoted by OptS The design variables and constraints of the optimal one are listed in Table 2. As shown in Figure 21 , the first peak wave moves backward in the vicinity of the bow and the tail peak wave maximum amplitudes of the optimized hull are obviously smaller than those of the original hull. In the optimization based on the whole speed range, the design area and the hull deformation are consistent with the previous text.

Therefore, the design variables and functional constraints drainage volume and wet surface area will remain unchanged. The solution set of each subobjective function is shown in Figures 22 � For the optimization objective function of KCS at the design speed point is the subobjective function F 4 , only the solution sets of the other subobjective functions relative to the design speed objective function F 4 are showed in Figures 22 � In Figures 22 � 25 , the feasible solutions are shown together with the infeasible solutions beyond the constraints.

At the same time, the convergence courses for various design variables of optimization are shown in Figure The convergence course of whole speed range optimization for various design variables: a dx 1 , b dy 1 , c dy 2 , d dy 3 , e dy 4 , f dz 1 , g dz 2 , h dz 3 , i dz 4 , and j dz 5.

Comparison of the transverse section lines between the optimal schemes Opt01 and Opt02 and the original hull is shown in Figure It can be seen that, compared to the original hull, the bulbous bows of Opt01 and Opt02 stretch forward and fullness is reduced. The upper end of the transition region of the hull is gradually recessed, while the lower end connecting with bulbous bow is gradually protruding outwards.

At the same time, the aft ends of Opt01 and Opt02 translate along the Z axis positive and the overall shape becomes more slender.

The total resistance of the optimized hulls based on different optimization algorithms and original hull at various Froude numbers are calculated by the method mentioned above and listed in Table 4. Comparison of the hull forms: a optimized hull form Opt01 blue and original hull form red ; b optimized hull form Opt02 blue and original hull form red.

The total resistance of the optimized hulls based on different optimization algorithms is all less than that of original hull at various Froude numbers smaller than 0. The resistance reduction effect of the optimal scheme OptS01 based on design speed is better than that of the two optimal schemes Opt01and Opt02 based on all speed range. But at the nondesign speed points, the resistance reduction effects of OptS01 are obviously worse than those of Opt01 and Opt02, and as the speed decreases the situation is more obvious.

The wave contours are compared for the optimal scheme Opt01 and original hulls for multiple Froude numbers on the left row in Figure Correspondingly, on the right row in Figure 28 , the wave contours are compared for the optimal scheme Opt02 and original hulls for multiple Froude numbers.

In Figure 28 , it can be seen that when the Froude number is small, the first peak wave maximum amplitudes of the optimized hull are obviously smaller than those of the original hull. With the increase of Froude Model Ship Building Kits Google Scholar number, the contrast difference is gradually reduced.

At the same time, the tail wave amplitudes of the optimized hull form are obviously smaller than those of the original hull under multiple Froude numbers. The optimal schemes Opt01 and Opt02 have similar law of comparison, and the difference is not significant. In summary, despite the comparison of the total drag coefficient, the comparison of the surface wave shows that the resistance performance of the two optimization schemes is better than that of the original hull.

At the same time, it is verified that the resistance optimization design methodology for bow and stern line considering whole speeds range is feasible and reliable.

A resistance optimization design methodology for bow and stern line considering all range of speeds has been implemented and applied. Firstly, the partially parametric mapping deformation method is presented via the features parametric curve. Accordingly the deformation theory formula has been put forward for launching the three-dimensional partial parametric hull deformation and geometry smoothing transition. Secondly, the method for evaluating the ship total resistance is proposed by combining the ITTC model-ship correlation formula with the potential flow Rankine source panel method.

By this method, the total resistance of KCS container ship is calculated which agrees well with the corresponding experimental data and further acquires validation with the overall error of 2. Accordingly the ship bow and stern of KCS have been optimized under conditions of the single design speed. The optimization results show a decrease of 7. The reason of drag reduction is analyzed through the comparison of wave profiles for the original and optimized hulls.

Then the ship bow and stern of KCS have been optimized under conditions of whole speeds range and two optimal schemes are obtained. The optimization results are comprehensively analyzed by comparing the total resistance and the wave profiles between the original and optimized hulls. Through the analysis, it can be seen that when the Froude number is in 0.

Overall, the drag reduction benefits of the optimal scheme based on whole speed range are not as good as those based on the design speed, but more balanced. Especially for modern container ships, its operating condition is often not fixed. In order to save energy, the measures of reducing speed are often adopted, and the ships rarely sail at design speed.

Therefore, while there is no special requirement or definite limit, the resistance optimization design methodology considering whole speeds range present in this paper can provide some guidance in early stages of ship design.

In conclusion, the present study shows an effective approach for the resistance optimization of modern container ships design which considers whole speed range and offers constructive assistance for designers who are attempting to obtain superior resistance performance through optimized designs. The data used to support the findings of this study are available from the corresponding author upon request.

The authors thank the reviewers for their comments and suggestions in improving the quality of the article. This is an open access article distributed under the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Journal overview. Special Issues. Academic Editor: Giorgio Besagni. Received 02 Feb Revised 31 May Accepted 13 Jun Published 08 Aug Abstract The main objective of this article is to describe an innovative methodology of synchronous local optimization which considers the whole ship speed range being presented for a KRISO Container Ship KCS. Introduction Energy saving and low-carbon environmental protection are the two inevitable trends in shipbuilding industry.

Hull Form Transformation Method 2.

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